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Blast from the past, restore,repair&rebuild

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  • Blast from the past, restore,repair&rebuild

    While digging trough old stuff, I've found a box with my old models from the 80es and early 90es. They brought a lot of memories so I've decided to return the favor by restoring them to the proper condition. First one to hit the "shop" is MiG 21 MF, from KP models, bought and built in 1992. The kit itself was an old soviet style kit, pretty crude and raw. In addition, I was impatient and inexperienced, without tools and references and the overall result was a mess.

    Not anymore. Seeing it again, I got nostalgia wave and decided to give it a second chance.

    So, the first thing for me to do is to remove the paint, than disassemble it. So, here I go, down the nostalgia lanes.

    1. Step one, paint removal.
    Attached Files

  • #2
    After the first bath in isoprpyl and de greaser, the glue came loose so I was able to disassemble the airframe without any problems. Paint, being 31 years old, turned to be more stubborn but I will get there.
    Attached Files

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    • #3
      Day six of the paint removal...I am getting closer to the end of initial preparation for the servicing.
      Attached Files

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      • #4
        Kind of late now, But....
        I've seen/read lots of modelers will spray the model with oven cleaner then put it in a airtight bag. S

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        • #5
          Originally posted by Gun Grape View Post
          Kind of late now, But....
          I've seen/read lots of modelers will spray the model with oven cleaner then put it in a airtight bag. S
          Yep, that is the procedure. However oven cleaners that we have here are super toxic and very dangerous if inhaled. I am using the milder one that can only blind me :) The thing is with these corrosive chemicals is that, yes they are intended for home usage but in these matters we are using them in super concentrated form and that is the thing that makes them so dangerous. I am using plastic containers instead of bag.

          Anyhow, the paint removal is drawing to a close and than I will move to the next phase.

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          • #6
            With the paint almost all gone, it is time to inspect the parts and take notes of the problems that they have.

            1. The canopy.

            Canopy had issues before the assembly. It is crude and inaccurate. Details are poor and its single biggest drawback is that it is a single piece part. So from the start it was a problematic part. To make matters worse, at the time it was bought, which was the summer of 1992, Yugoslavia was placed under sanctions and that meant shortage of almost every kind of imported items. Modeling cement and glue included. Since my father was a chemist, he proposed usage of chloroform as a glue and it worked really well on polystyrene plastic. Problem was how to apply it without damaging areas that are not supposed to be glued and that lead to the canopy being ruined even further. The chloroform spilled over while I was holding it and melted huge part of the canopy.
            So for the canopy part, removing the damage caused by the acid is the first step. Now, I never liked it in its original form, so after the polishing is done, it will be leveled up a bit.

            2. The wings.

            Wings suffer the same problem as the canopy but they are a bit easier to deal with. The damage caused by acid will be sanded and polished, panels and rivets will be engraved afterwards and the landing gear bay will be cleaned and fixed as well.

            Fuselage is still soaking as it has some really stubborn paint areas but its almost done.

            But man, just holding it it brings so much nostalgia and memories. Its like the very essence of those times got embedded into it. To bad that none of them are good, which kind of reflects the sorry state that its in now.
            Attached Files
            Last edited by Versus; 05 Mar 23,, 18:11.

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            • #7
              Ick...

              You might be able to find a vacuform canopy for it.

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              • #8
                Originally posted by Zad Fnark View Post
                Ick...

                You might be able to find a vacuform canopy for it.
                That is one of the last resort options, if sanding and polishing doesn't work. I will see, there many options to consider in order to solve this problem. But yea, the situation is bad. That is the only positive thing in this project, it can't get worse than this.
                Last edited by Versus; 06 Mar 23,, 16:16.

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                • #9
                  Unfortunately the damage from the acid was too great and one piece of canopy broke off. I was able to glue it back together with super glue but the canopy itself is unusable in its current form. So the next move is to make a new one. The original canopy will be used for casting. At this moment the resin is in preparation phase, it will take a week for it to be useful. For the mold, I was able to get my hands on the "blue stuff" but before it, I would like to try a different approach with materials that were available to me at those times. Stay tuned.

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                  • #10
                    The damage on the canopy. The acid went deep into the clear par so that it cannot be polished. That was the moment when I went a bit too far and broke the piece. But its fixed now and ready for the new purpose, as a pattern for the mold.
                    Attached Files
                    Last edited by Versus; 12 Mar 23,, 08:34.

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                    • #11
                      And Mr.Spur that will be used for fine details. The spur will be heated until it gets soft enough so that it can be extruded to fine plastic lines. Than those plastic lines will be used to rebuild the framework for the cockpit. Also this method will be used for making wheel struts, antennas and other micro parts. The draw back of this method is that parts are far more brittle so they have to be handled extra carefully. I will post pictures of the procedure later this day.
                      Attached Files

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                      • #12
                        A work pop up so I decided to do test thermal forming now. Here are results using only a candle with open flame. In order to avoid plastic being set on fire, I am going to heat it but in a metal tube and for that I am going to make a simple rig just to hold the metal tube over a heat source that will allow more controlled melting of the plastic. The temperature regulation will be done by lowering or rising the candle from the pipe. Primitive but hopefully it will work. :) With this method you can go way below 0.5 mm with plastic extrusion and than re heat it if you need more complex shapes. It can be polished too but you have to be super careful with it.
                        I've checked the compound for the clear parts and its forming nicely.
                        Attached Files
                        Last edited by Versus; 12 Mar 23,, 10:38.

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                        • #13
                          Never could master the art of stretching sprue. It takes a steady hand and patience to get a consistent pull. .

                          Once upon a time I had a canopy that got doused in MEK..

                          A final option is to use the canopy but paint the clear areas blue/black.. Make it look like the old wood desktop display models.

                          Click image for larger version

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                          • #14
                            Originally posted by Gun Grape View Post
                            Never could master the art of stretching sprue. It takes a steady hand and patience to get a consistent pull. .

                            Once upon a time I had a canopy that got doused in MEK..

                            A final option is to use the canopy but paint the clear areas blue/black.. Make it look like the old wood desktop display models.

                            Click image for larger version  Name:	Grumman-F-14-Tomcat-Jolly-Rogers-Revised-++-PA-1-Model.jpg Views:	0 Size:	48.8 KB ID:	1597855
                            Yea, it is a touchy process but necessary with this type of damage. However, this restoration is just a warm up for the real mess which is AH 1-T, now that one will be super challenging but I am committed to it. Servicing M-197 gun turret gives me nightmares...
                            Last edited by Versus; 12 Mar 23,, 20:24.

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                            • #15
                              Chemical brothers...
                              Compound made out of dissolved Styrofoam in acetone, forms polystyrene mass that is very soft and can be used for casting plastic parts but that has to be done quickly, under 10 seconds because it hardens super fast. However, the plastic from pure Styrofoam is hard and very brittle so in the next experiment I will try to make it more softer by mixing it with dissolved spur goo.The more transparent goo is plexiglass also dissolved in acetone, that will be used for casting clear parts. It takes around a week for it to reach completely transparent state.
                              As usual, if you want to try this method, do it in well ventilated space and wear protective gear (cover for eyes, mask and gloves) because fumes are toxic and corrosive.
                              Attached Files
                              Last edited by Versus; 15 Mar 23,, 07:30.

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